Which of the following quartic functions has x=-1 and x = -3 as its only two real zeros?

y=x^4 - 4x^3 - 4x^2 - 4x - 3

y = -x^4 + 4x^3 + 4x^2 + 4x + 3

y x^4 + 4x^3 + 3x^2 + 4x

x^4 + 4x^3 + 4x^2 + 4x + 3

Respuesta :

frika

Answer:

[tex]y=x^4 + 4x^3 + 4x^2 + 4x + 3[/tex]

Step-by-step explanation:

Consider function [tex]y=x^4 + 4x^3 + 4x^2 + 4x + 3.[/tex]

Factor it

[tex]y=x^4 + 4x^3 + 4x^2 + 4x + 3\\ \\=x^4+x^3+3x^3+3x^2+x^2+x+3x+3\\ \\=x^3(x+1)+3x^2(x+1)+x(x+1)+3(x+1)\\ \\=(x+1)(x^3+3x^2+x+3)\\ \\=(x+1)(x^2(x+3)+(x+3))\\ \\=(x+1)(x+3)(x^2+1)[/tex]

This function has two real zeros [tex]x=-1[/tex] and [tex]x=-3[/tex] and two comples zeros (because [tex]x^2+1[/tex] cannot be factored futher).

Hence, the function [tex]y=x^4 + 4x^3 + 4x^2 + 4x + 3[/tex] has [tex]x=-1[/tex] and [tex]x=-3[/tex] as its only two real zeros.